Insert parts or fastener elements, hereinafter “insert parts” of the kind specified may be configured either as stoppers for tight closure of a wall opening on a vehicle body or as dowels intended to accommodate a fastening element, for example a screw.
An insert part of the specified kind, configured as a stopper, is disclosed in DE 31 00 498 A1. This stopper comprises a neck engaging the opening and having a plurality of interruptions. In the interruptions, spring engaging elements are arranged, each of which possesses an inclined shoulder. If the stopper is inserted in the wall opening, the shoulders bear on the edge of the opening on the side away from the flange. In this way the flange is pressed in the direction of the wall, and the body of sealing material projecting from the depression in the flange is subjected to pressure. If the inserted stopper is heated to a suitable working temperature below the melting point of the material of the stopper, the body will melt, while the pressure exerted draws the edge of the flange against the surface of the wall and the molten sealing material flows through the sheet-metal opening and fills up the space between the edge of the opening and the neck portions of the stopper. Here it is disadvantageous that the position of the stopper will be altered upon melting of the adhesive, and undesirable deviations of position may result. Furthermore, the molten sealing material may emerge at the circumferential edge of the flange, so long as the circumferential edge is located at a distance from the wall. The application of the known stopper is therefore substantially limited to horizontally oriented walls.
DE 44 23 576 C2 describes a closure having a body of molded adhesive, inserted in an opening arranged in a metal sheet. The body has a circumferential edge that rests on top of the sheet, on the metal edge around the opening. By a plurality of elastic catches, the body is retained on the metal sheet. On top of the circumferential edge of the body, a string of adhesive is laid down. The adhesive, melted by heating, passes through holes in the circumferential edge into a groove on the under side of the edge in contrast with the metal sheet, so that the groove can fill with adhesive to form a firm connection by bonding between the body and the sheet. This closure too is suitable only for openings in walls substantially oriented horizontally.
Such fastening elements are secured against rotation by the neck in the opening of the wall, and may therefore, upon screwing of a fastening screw into the bore, transmit a counter-torque to the wall, opposing the torque that rotates the screw. With the aid of the catches, they are secured against pulling out of the opening. To achieve as strong an axial retaining force as possible, known fastening elements of the kind specified are provided with spring catches on all four sides. Here it has been found that only a limited counter-torque can be achieved for the screwing in. If adverse deviations in dimensions of screw or bore encounter each other, an overrotation of the fastening element and hence an impairment of the assembly operation may result.
The object of the invention is to create an insert part of the kind initially specified, that makes possible the observance of close positional tolerances and suitable also for application to inclined walls. A further object of the invention is also to create a fastening element of the kind initially specified, that, with adequate axial retaining force, can transmit as high a torque as possible to a wall.